m 
BRITISH PHARMACEUTICAL CONFERENCE. 
add bichloride of platinum, and evaporate to dryness. If soda be present, you 
will have acicular crystals of the platino-chloride; or if potash be there, you 
will find cubical crystals of the corresponding salt. Thus, in a few minutes, by 
the aid of the microscope, no less than seven distinct salts may be readily de¬ 
tected, besides a great number of others. 
So extensive, indeed, are the uses that a chemist might make of the microscope, 
that a general paper would be of an unreasonable length. The author, there¬ 
fore, now has confined his paper to that part of the subject only which relates to 
the detection and examination of the soluble salts which form definite crystals. 
The microscopist takes advantage of the fact that each salt takes in crystal¬ 
lizing its own particular form. Like the botanist, who finds in the shape of a 
leaf or some appendage a reliable guide to the specific distinction of the plant, 
he finds the same observation to hold good with all the varieties of crystalline 
form. So universal is this aptitude for a particular configuration, that few sub¬ 
stances exist in nature which have not the faculty of each assuming a form pecu¬ 
liar and constant to itself. Such, indeed, is the explanation of what the chemist 
terms u crystallization.” 
Few fluids can be found, whether natural or artificial, whether a secretion or 
a chemical solution, that do not contain substances which, by some means or 
other, may be made to separate as crystals. Now, as these crystalline attributes 
are so universal and constant, the author has founded on it his method of deter¬ 
mining the name and nature of the crystalline constituents of a given fluid,—a 
method by which, without any chemical test, but simply a microgoniometer, 
the name may be determined. 
Crystals may be obtained from a given solution for microscopical purposes in 
six different ways, no matter how small the quantity may be :— 
1. By simple deposition by cooling; as the well-known triple phosphate, so 
often seen in animal secretions. 
2. By precipitating a salt in a comparatively insoluble form ; as the sulpho- 
cyanide of strychnia or bitartrate of potash. 
3. By fusion ; as in the case of salicine and several of the alkaloids. 
4. By galvanic deposition ; as in the detection of lactic acid. 
5. By sublimation ; as in arsenious and benzoic acids, thein, etc. This method 
has been lately used by Dr. W. A. Guy, who seems to have been very successful 
with the alkaloids. 
6. By evaporation. 
In all the previous methods the object usually is to obtain separate and cha¬ 
racteristic crystals, whose natures are only to be known by their peculiar form 
or confirmative testing. By the mode now to be described the author has ob¬ 
tained certain results which, as they have not hitherto been published, he wishes 
to lay before you, hoping that to some they may prove useful. 
A drop of the given solution is placed on a glass slip, and slowly evaporated 
over the flame of a spirit-lamp, or in a drying chamber. A crystalline residue 
is left which, to the eye only, appears simply a magma of crystals without any 
definite arrangement. From a careful study of these, considerably magnified, 
the author noticed a certain arrangement of lines peculiar and constant to every 
salt. Again, on every slide it will be noticed that two angles always predomi¬ 
nate over the others, and that the same salts have these two angles invariably 
the same. It is thought, therefore, that a table might be constructed from 
these angles, so that a measurement and reference to the table would give the 
name of the salt. A specimen of this table is before you. It will be evident 
that the compilation of such a table would involve the execution of an immense 
multitude of observations, and a great expenditure of time. 
Let us now proceed to an examination of one or two salts, sketches of which 
you have on the table. 
